Ubiquitous network access has been almost realized today. From network infrastructure point of view, different networks belong to different layers (e.g., distribution layer, cellular layer, hot spot layer, personal network layer, and fixed/wired layer) that provide different levels of coverage and connectivity to users. Because the coverage of a specific network may not be available everywhere, and because different networks may be optimized for different services, it is thus desirable that user devices support multiple radio access networks on the same device platform. As the demand for wireless communication continues to increase, wireless communication devices such as cellular telephones, personal digital assistants (PDAs), smart handheld devices, laptop computers, tablet computers, etc., are increasingly being equipped with multiple radio transceivers. A multiple radio terminal (MRT) may simultaneously include a Long-Term Evolution (LTE) or LTE-Advanced (LTE-A) radio, a Wireless Local Area Network (WLAN, e.g., WiFi) access radio, a Bluetooth (BT) radio, and a Global Navigation Satellite System (GNSS) radio.
Due to scarce radio spectrum resource, different technologies may operate in overlapping or adjacent radio spectrums. For example, LTE/LTE-A TDD mode often operates at 2.3-2.4 GHz, WiFi often operates at 2.400-2.483.5 GHz, and BT often operates at 2.402-2.480 GHz. Simultaneous operation of multiple radios co-located on the same physical device, therefore, can suffer significant degradation including significant in-device coexistence (IDC) interference between them because of the overlapping or adjacent radio spectrums. Due to physical proximity and radio power leakage, when the transmission of data for a first radio transceiver overlaps with the reception of data for a second radio transceiver in time domain, the second radio transceiver reception can suffer due to interference from the first radio transceiver transmission. Likewise, data transmission of the second radio transceiver can interfere with data reception of the first radio transceiver.
A new IDC indication message comprising two options is provided by LTE Rel.11 to avoid potential radio interference within the same device. Under FDM (Frequency Division Multiplexing) option, a user equipment (UE) reports interfered frequency and the network moves the UE away from the troubled frequency by handover. This option provides a quick approach with almost no performance impact at the expense of possible LTE spectrum waste. Under TDM (Time Division Multiplexing) option, a UE suggests LTE TX pattern to the network by DRX (Discontinuous Reception)-like gap, subframe bitmap gap. This option provides the best spectrum efficiency with full range LTE B40 and Wi-Fi 2.4 GHz operation but suffers performance impact on throughput due to time-sharing between radios. Internal coordination between LTE and Wi-Fi modules is also needed to determine LTE DRX pattern.
For LTE cellular data and Wi-Fi P2P technology coexistence scenario, the two systems execute by turns in DRX-based IDC solution. LTE data scheduling is described by a set of DRX parameters, while Wi-Fi P2P data scheduling is described by Opportunistic Power Saving (OppoPS) and Notification of Absence (NoA) parameters. Each of the parameters must be selected carefully to maximize efficiency. Without proper alignment, performance degradation due to Wi-Fi internal scheduling constraint will affect the system performance significantly.